Electrodeposition of nickel



Ff i

Patented Dec. 25, 1951 No Drawing. Application August 2711938; Serial No. 46,560

nclsimsi (o1; 204-49),

This; invention" relates to new and" useful im provements inthaelectrodeposition otnickel or combinations. oft-nickel and cobalt.

This application isa continuouatiomin-part; of-

myjapplicationrserq No; 7642897fi16dJi11y3Qg 1947; now abandoned.

Manyiattemptsrhavebeen made' to: produce nickel depositsi thatl-d'oi not require bu'fiing: atter: plating; When the: metal: surface; on v whichlthe: nickel is deposited: has: as smooth enough finish; itiis sufficientito putson a" nickel. deposit produc ingggood' speoular reflectiom- Thisiisrthe type'iof deposit that theplaten callsi bright nickel'i Its fieldxof. applicationaisfi chiefly: onibufied brass-and copper:

Ifz. themetal; surface": on which: bright niclteliis deposited is: not freefrom scratches and die marks; these may show up in: the bright: nickel deposit; in fact; contrast withfthe surrounding bright: surface: may make such imperfections stand outeven more than they do in the unplateti surface-.- seratches and die marks are more likely to; be": foundlion steelibecause-theyare mcre diffi cult toxpolish out on steel: than :on brass or cop'per; The use of bri'glit nickel on "steel is =therefore less advantageous thanit is on brass or copper; Bufi ingvtheabri'ght nickel does not help matters m'ueh becaalserbri'gh ti nickel:deposits do not fl'ow rea'dily under the *pressureemrtediii the buffiriig opera=- tion? and: therefore bumng thewbright riickel does not satisfactorilycoverup scratches andi die marks; 7

Even when brightinickel is i applied over brass 01'? copper, bu-fiing lines may show through on careiullexaminationi- This is especiallythe" case when the: finishingoperations have been?- per formed by careless or unskilld workmenpr when an :essential step in finishing is omitted for the sake of economy.-

Thus; whether thei deposit is' to be bu'fied or not, -it: is desirable to produce deposits if possible which coverup linesy scratches and marks of any description that are present in the sur fa'ee to :be platdl Ifthe deposit isto be buffdi furthermoreith is desirable to produce deposits with characteristics which make for- 'easy bufii'nga- Ghe' object of th'epresent" invention is' a method of i producing electrodeposits containingnickel or an alloy of cobalt and nlckel that is more readil y bu-fl ed their ordinary depositsot the same metal.

Another object ot the: 1 present invention is: a' method of producing-i electrodeposits containing ni'ckel or an alloy of colml-t and: nickel that dl pzinish the roughness of the-starting "surface and 2" reduce the amount. of plating;

Another object on the present invention is a method of: producing; either bright or grayelec:

trodeposits containing; nickel; or an -alloy of cobalt and niekel that diminsh the roughness of the starting surface'and reduce'the amount of polishing or finishing. required preparatory toplating.

Still further objeots and; advantages Wi1l-appear from the: more" detailed description given below:

I have found that the; bright nickel plating solution described b'yWe'i'sb'ei'g and Stoddard in U; swPatent No. 2,026,718 can be modified to give deposits with. superior buffing-characteristics and withabilityto smooth. out. linesp-scratches; die marks and various other defects' 'in the "surfaces overwhich they are applied. This improved type of deposit lends itself to a-variety of applications.

For example the cost of polishing steel, nickel plating in' this'iinpro'ved s'oliitioii, aii'd'the'ri biifl ing' the nickel is lower tli an that (ii any alternative procedure of whioh}I-am aware There is a; two--fold ativantage fiifst; a lare' proportion of the polishing liries 'ii-i' the-steel-aresmoothed out or erased, thus-redncingthe amount-oi nickel buffing: required; and in the second place, the nickel deposit itsel-t' is! easier to biifi than ordinary electrodepositedxnickele Thus savings in the over all eostof producingaeceptable nickel plated steel can bebroughtizabout by-utilizing'sthepresent invention In the foregoing example -the platingt conditions are usually chosemsoas-to g ive r a-deposit that not bright; because that a type of; deposit has other properties==- whichmake it especially suitable for certain applications, such as automobile bumpers. For pIatin"g"on brass or copper, a bri'g ht-deposit would generally be preferred. The useof my improvedsolution for producing a brightdeposit --OIl-b1' aSS--Ol coppehwo'i'ild "make it possible to reduce the finishing: work done preparatory toplating, becausethe plating opera' tion itseltwould--smooth-out certain "lines and defects that would other-wise have to be taken out before platlnge v Normally a nickeldeposit may cause some illcrease the roughness of thesurface treated and does not generally inipro'vethe smoothness of thesurface'to whichit isappli'ed. The smooth ness before and after"ti'eatment"can'be'deter minedv byrus'e: 01-" the brush-Surface Analyzer" or "a =Profilometer2" The brnshiisnrtace analyzer p'rocluces a chant which shows graphically the A buffing: required-- after peaks and valleys on the surface. Hence by application of this device to the original and plated surfaces a quantitative comparison of the smoothness of the surfaces can be obtained.

On examining numerous samples of surfaces of the improved deposits above referred to by means of a brush surface analyzer and comparing them with the original steel surfaces before plating, I have found that the nickel deposit tends to' cover up or smooth out scratches and other imperfections in the original surface. Furthermore, I have found that this improved coating produces a far greater smoothing. action than ordinary coatings of gray nickel or bright nickel. This deposit therefore shows a double advantage. It is not only easier to buff, butless buffing is required than with ordinary nickel.

I have also found that the smoothing actionvalue is preferred, because the results obtained are somewhat better and because solutions with high nickel sulphate content are more strongly buffered against pH change.

The principal function of the chloride is to promote good anode corrosion. The amount stated is suflicient. considerably more or less may be used without particular effect, for example, from 15 to 60 grams per liter.

Boric acid may vary from 30 to 40 grams per liter.

Formic acid may vary from to 30 grams per liter; The lower amount is essential for good smoothing action. Any increase beyond that has little effect on the smoothing action, but is desirable where brightness is required.

can be further increasedby the addition of certain substances, as hereinafter described, and

that the smoothing action maybe adversely affected by failure to exclude certain other substances. Some of these addition agents, when used by themselves,- produce brittle deposits which are often pitted, but when .used in conjunction with my modified solution, excellent physical properties are obtained alongwith the desired smoothing action and no pitting.

The preferred composition of a water solution for producing semi-bright deposits in accordance with this invention is given as Example I.

Example I Gramsper liter Nickel sulphate 360 Nickel chloride 30 Formic acid Boric acid 40 Cobalt sulphate"; 3 Formaldehyde (anhydrous) 0.0-0.5

The preferred operating conditions are: Temperature 70-75 degrees centigrade pH (electrometric)- 2.3 7 Current density 40 amperesper square foot Agitation Vigorous The conditions above set forth represent the optimum for producing nickel, orrather cobaltnickel, deposits that are easy to buff and have a powerful smoothing action so that the total amount of work required-to-buifthe plated deposit to a high lustre is less than for ordinary nickel. The deposits so obtained, moreover, are extremely ductile and free from pits.

The preferred composition of a water solution for producing bright deposits inaccordance with this invention is given as Example II.

In both examples, the content of nickel sulphate may be varied over a wide range, say from 120 to 400 grams per liter.. A relatively high The cobalt content is kept at the lowest figure practicable in order to keep the cost down. The

quantity indicated corresponds to a cobalt con- 7 tent of about one per cent in the deposit. A small amount of cobalt has considerable smoothing action; large amounts produce additional smoothing but not in proportion. amounts of cobalt are therefore not. economical. Somewhat less desirable results are obtained if no cobalt is present. Thus the content of cobalt compounds may vary from no cobalt to any amount which is economically justifiable. quantity of cobalt indicated in Example II is sufficient to produce bright deposits when the solution is reasonably free from impurities. Somewhat greater tolerance for impurities may be gained by increasing the cobalt.

Formaldehyde does not have any marked effect on the smoothing action. It is helpful in con-.

, trolling pitting and is necessary for brightness,

as in Example II. The amount required to control pitting depends on the condition of the solution with respect to impurities and other operating conditions. The preferred amount required for bright deposits is 1 gram of anhydrous material per liter but may vary from about 0.7 to 1.5 grams per liter. The amount of formaldehyde used may therefore vary all the way from none up to about 1.5 grams per liter according to the purpose forrwhich the solution is operated.

In comparing the composition of the foregoing solutions with that in the Weisberg and Stoddard patent previously referred to,v it is to be noted that formaldehyde which is the primary brightening agent in the patent, is not a factor in pro-v ducing smoothing action and may or may not be used in the practice of my new invention. A further difference is that ammonium sulphate, which is recommended as an auxiliary brighten ing agent in the Weisberg and Stoddard patent, is omitted altogether. Since even small amounts of ammonium sulphate have been found to exert an unfavorable effect on the smoothing action, the solution shouldbe free from ammonia and ammonium salts in amounts which will deleteriously affect the smoothing action of the deposited nickel. Moreover, I have also found, so far as brightness is concerned, that ammonium sulphate is not required if the solution is sufficiently free from impurities. I

In regard to operating conditions, the temperature may vary from about 60 to degrees centie grade. Below 60 the smoothing action is diminished; above'80 the smoothing action continues to improve, but the deposit tends to become'hard and brittle. Itis believed that the impairment in physical properties is due to the fact that for-v mic acid becomes rather volatile under these ex-. treme conditions and is lostfrom. the solution.

Larger The.

.skilledin theart:

' The pI-Jlrange may vary from? about- ,10, to. 4 The best; range for semiebrlshtplate-nis 2i1=:to, 2:5;- for bright plate 3W5; to 33 1s preferable; The smoothing action has been found; to be substantially independentof: whether thahighen onlower pH range is employed.

In general, the smoothingtactiondecreaeeswith increased current density; othee conditions re maining the same. An average of,-'40 to50iam. pers per square foot may.be usediom-mostkinds of work with suitable agitationi Unden favorable conditions, good smoothing-t a tion been ob: tained at current densities" as high as; 19.0: amaperes-per square foot, t

The addition on magnesium suiphata to the preferred solution upto 150* g mme liter on more improves the electrical conductivitytot; the solution and is useful, in loweninga power consumption where higher current densitiesiare em-,

ployed. Addition-- ofmagnesium sulphate-ion: this. 20 purposeis notdetrimental totthe smoothing action and b uffabilitynor tothephysical propenties of the deposit. The following examples illustratepreferred compositions containing magnesium sulphate, III being-asolution that; giues semic-i. bright deposits and IV a solutiom that: gives brightdeposits Ezamplellii C alts i h t.

Ma nesi m i at; Formaldehyde (anhydrousi er liter ntiiii a L0. amnt ssner auaza oe r 4 e a f -a r-s-t mmplc 1M:

Nickel sulphate n 3 Nickel chloride 30 Agitation of the solution ormovingmhe worki; with respectto the solution has anappreciable effect on the smoothing action and-bufiability of h deposit PFQlI'P" agi at on. s; tsita e: o best results.

The presence ot dissqlved impurities in the solution may interfere with thes nogming agtion of the solution or! make the ideposits hard rtg bvumb sid po ibly im airinadb h dear bit qu i of he taes t'. Suspended meuri ies should likewise ibeavoided, 'Ifhe splution must therefore be purified and filtered with sgrup are r e ti t i i 1 s f9 a ivi nickel n a neso c cantor;

Qhr mime a unner-sew: a lrpnifeu o s) .r ,7

The q c anceior ferr ciiro i sab ut nemies ired; imes hi er than for. terrous irons and cadmium are som what;- beneficial cert in onoontraticms,vv ut he r cli nt, on: when: nroperties akes it.;. esirab toi x udehcm-i he efieets. ofor anicimpu ties arepmoreid flie cult to describe specifically because th are y p s le purities to consider Asianeisr M -Pla t maybe. mentioned that atraee 0i: issnficient to cause c mplete loss oi-smo hi. eifegt. Qareis e essery toavq dc nta x i me the solution, n efirs np ac B sides is; Peri:- odia or continuous; treatment with activated; carbon is necessary to maintain favorable qOnd t, tions for operation. In general,- good smoothing action is obtained only when careful; attention; given to allop r in -requirements asd sc hedi herein.

h smoothin action of he. nickel: d posit; herein referred to canibe obtained by adding cerrt taint other substances,- notably coumarin. o! at typical Watts nickel plating solution: having-the following composition Grams pen liter;

However, under the most favorable conditions, of op ration he depositobta nedm cro h solu- 199 15 rd n rittle as o e ndesitablev for most pur oses where n ckelhisapplied I have, found, though, that the addition of, coumarin to the improved. solution as, hereinbeior e d.escrihe,d enhances the smoothing action of thedeposits pr duced therefrom f: the a ountoi cpwnarin adde s o ssiv hecde os tsioh ainedi this way i have good physical properties as well superior smoothness.

n ci i sulpha es-"u c- Oe msr rL- tea litkeltchi ride we, Oemm 112 a it r;- iitkel o ma rr-var ms-pe iter Eer e-at l er?! e-s- Q rams, n r ee Qohalt: illp tess-r-s rams,p rtcn Forma hyde (anhyd u =)1-.--;.- --H-. he am, perz itea Goumar m-qin 1;.0eramp rlite1's mp t -a 0 de e scentigradei Cm'rent density---- 40 amneres p er;sq.'.foot@; pH-(electrometric) 2.3

Agitationnns Vigorous.

Examplevr Nickel=;sulphate. s- 3.60grams perliten Nickel chloride SOgramspenliten Nickel-formate agrams per-1iter Boric acid; vgramsper liter Cobalt sulphate 3igramszperiliten Formaldehyde (anhydrous); 1.0 g-ramper liter Coumarin 1.0 gram,per1iter= Temperatures degrees-centig'rade Current densityi. 40amperespersq ifoots pH (electrometric) 3.7 i

Aeitati on leomuai Preceding comments concerning ranges of proportions of the various constituents of the bath and operating conditions apply to Examples V and'VI.

. The'solubility'of coumarin in the nickel p1at-' ing solution is 10w but increases rapidly with the temperature; Coumarin is 'plated'out of the solution" fairly'rapidly so' that it must be replaced regularly, or better still continuously, as the solution is used. This may be done by circulating the solution, or part of it, through a filter charged with-coumarin. The content of coumarin can be controlled at the desired point by saturating the Solution at any desired temperature and circulating as-much of the solution through the filter as may be necessary. y

v The amount of coumarin required in the solution'is small. The optimum content of coumarin for the purpose of this invention is in the neighborhood of one gram per liter or even less. A noteworthy feature in regard to the smoothing action'of the nickel and cobalt-nickel deposits herein described is the 'fact that the smoothing action increases with increasing thickness 'ofdeposit, at least over the range I have investigated. If the nickel thickness is 0.002 inch, the smoothing action is more pronounced than if the thickness is only 0.001 inch. If the thickness of the deposit is increased to 0.003 inch, there. is a further gain in smoothness.

The term nickel" in the accompanying claims includes the possible presence of small amounts of cobalt. The term smooth as used in the claims refers to a deposit the surface of which is smoother than the. surface on which the deposit is applied, the specific test being made by means of a brush surface analyzer.

, The foregoing description is given by way of explanation and illustration only, and not by way of limitation. Various changes may be made by those skilled in the art without departing from the scope and spirit of the present invention.

j I claim:

The method of electrodepositing nickel to produce smooth, ductile, easy-bufilng deposits which comprises electrolyzing a body of a solution containing as essential constituents nickel sulphate 120 to 400 grams per liter, nickel chloride to 60 grams per liter, formic acid 5 to grams per liter,-and boric acid from 30 to grams per liter, the solution being freeof ammonia and ammonium salts in amount which will deleteriously affect the smoothing action of the deposited nickel, and free from impurities in amounts of not more than 5 milligrams per liter of aluminum, nor more than 1 milligram per liter of chromium, not more than 20 milligrams per liter of copper, and not more than 1 milligram per liter of ferrous iron, purifying said body of solution with respect to said impurities, the frequency of said purification and the extent thereof being such as to maintain the purity of the solution, during electrolysis, within said limits, maintaining the pH of the solution, during elec-. trolysis, between 2 and 4, and discontinuing. the electrolysis before the electrodeposited nickel has exceeded a thickness substantially greater than 0.003 inch, whereby deposits are obtained which are ductile, easily buffed, and have a surface sub: stantially smoother than the surface of the oathode on which they are deposited.

,.2.,-The method of claim 1 in which the solution; is electrolyzed at a temperature between 60 C. and 80 C.

3. The method of. claim 1 in which the solo-- tioncontains'formaldehyde up to 1.5 gramsper liter, and in amount suflicient to impart increased-brightness to thedeposited nickel.

.4. The method .of claim 3 in whichthe, solution is electrolyzedat a temperature between 60 C. and C.

. 5. The method of claim 1 in which the solution contains cobalt sulphate up to 3 grams per liter, and in amount sufficient to further enhance the smoothing action of the deposited nickel.

6. The method of claim 1 in which thessolution :contains .magnesium sulphate up to 150 grams per liter, and in amount effective torimprove the electrical conductivity of the solution.

7. The method ,of-claim 1 in which the solution contains approximately 1 gram per liter 01' coumarin. Y

8. An electrolyte for depositing a smooth, ductile, easy-bufiing coating of. nickel which comprises as essential constituents nickel sulphate to 400 grams per liter, nickel chloride 15 to 60 grams per liter, formic acid 5 to 30 grams per liter, boric acid 30 to 40 grams per liter and formaldehyde up .to 1.5 grams per liter and in amount effective to. impart increased brightness to nickel electrolytically deposited from the electrolyte, the pH of the electrolyte being between 2 and 4, said electrolyte being free of ammonia and ammonium salts in amount which will deleteriously affect the smoothing action of nickel electrolytically deposited therefrom and free from impurities in amount of more than 5 milligrams per liter of aluminum, more than 1 milligram per liter of chromium, more'than 20 milligrams liter of copper'anol more than 1' milligramper liter of ferrous iron. 7

9. An electrolyte fordepositing asmooth, ductile, easy-buffing coating of nickel which comprises as essential constituents nickel sulphate 120 to 400 grams per liter, nickel chloride 15 to 60 grams per liter, formic acid 5 to 30 grams per liter, boric acid 30 to 40 grams per liter, and cobalt sulphate up to 3 grams per liter and in amount eifectiveito'further enhance the smoothing action of nickel electrolytically deposited from the electrolyte, the pH of the electrolyte being between 2 and 4, said electrolyte being free of ammonia and ammonium salts in amount which will deleteriously afiect the smoothing action of nickel electrolytically deposited therefrom and free from impurities in amounts of more than 5 milligrams per liter of aluminum; more than 1 milligram per liter of chromium, more than 20 milligrams per liter of copper and more than 1 milligram per liter of ferrous iron. 10. Anelectrolytefor. depositing a smooth, duetile,-easy-bufling coating of nickel which comprises as essential constituents nickel sulphate 120 to 400 grams per liter, nickel chloride 15 to 60 gramsper liter-,- formic acid 5v to 30 grams per liter, boric acid 30 to 40 grams per liter and approximately 1 gram per liter of coumarin, the pH of theelectrolyte being between 2 and 4, said electrolyte being free of ammonia and ammonium salts in amount which will deleteriously affect the smoothing m ster nickel electrolytically depositedtherefrom and free from impurities in amounts of more than 5] milligrams per liter of aluminum, more; than 1 milligram per liter of chromium, moretlian 20 milligrams per liter of copper and more than 1 milligram per liter of ferrous iron. f V

11 An' electrolyte as defined in claim 10 whichv also 'contains'formaldehyde up to 1.5 gramsper liter and in amount effective to impart increased brightness to nickel electrolytically deposited Number from the electrolyte. 2,191,813 LOUIS WEISBERG. 2,196,588 2,449,422 REFERENCES CITED 5 2 70,775 The following, references are of record in the 1 1 Name Date Weisberg et a1 Jan. '7, 1936 Number 10 Name Date Brown Feb. 27, 1940 Hull Apr. 9, 1940 Smith Sept. 14, 1948 Jernstedt et a1 May 24, 1949 Stoddard Dec. 12, 1950 OTHER REFERENCES Transactions of the Electrochemical Society, 10 vol. 77 (1940), pp. 223-231. 

1. THE METHOD OF ELECTRODEPOSITING NICKEL TO PRODUCE SMOOTH, DUCTILE, EASY-BUFFING DEPOSITS WHICH COMPRISES ELECTROLYZING A BODY OF A SOLUTION CONTAINING AS ESSENTIAL CONSTITUENTS NICKEL SULPHATE 120 TO 400 GRAMS PER LITER, NICKEL CHLORIDE 15 TO 60 GRAMS PER LITER, FORMIC ACID 5 TO 30 GRAMS PER LITER, AND BORIC ACID FROM 30 TO 40 GRAMS PER LITER, THE SOLUTION BEING FREE OF AMMONIA AND AMMONIUM SALTS IN AMOUNT WHICH WILL DELETERIOUSLY EFFECT THE SMOOTHING ACTION OF THE DEPOSITED NICKEL, AND FREE FROM IMPURITIES IN AMOUNTS OF NOT MORE THAN 5 MILLIGRAMS PER LITER OF ALUMINUM, NOR MORE THAN 1 MILLIGRAMS PER LITER OF CHROMIUM, NOT MORE THAN 20 MILLIGRAMS PER LITER OF COPPER, AND NOT MORE THAN 1 MILLIGRAM PER LITER OF FERROUS IRON, PURIFYING SAID BODY OF SOLUTION WITH RESPECT TO SAID IMPURITIES, THE FREQUENCY OF SAID PURIFICATION AND THE EXTEND THEREOF BEING SUCH AS TO MAINTAIN THE PURITY OF THE SOLUTION, DURING ELECTROLYSIS, WITHIN SAID LIMITS, MAINTAINING THE PH OF THE SOLUTION, DURING ELECTROLYSIS, BETWEEN 2 AND 4, AND DISCONTINING THE ELECTROLYSIS BEFORE THE SUBSTANTIALLY GREATER THAN EXCEEDED A THICKNESS SUBSTANTIALLY GREATER THAN 0.003 INCH, WHEREBY DEPOSITS ARE OBTAINED WHICH ARE DUCTILE, EASILY BUFFED, AND HAVE A SURFACE SUBSTANTIALLY SMOOTHER THAN THE SURFACE OF THE CATHODE ON WHICH THEY ARE DEPOSITED. 